This invention relates generally to couplings for connecting two shafts which are misaligned and more particularly to a flexible coupling for the purposes described including thin, contoured, flexible diaphragm means.
Flexible couplings for connecting two shafts such as a driving shaft and a driven shaft, which transmit torque while accommodating axial extension and angular misalignment of the shafts have long been used in aircraft, industrial and military applications. These couplings use at least one but more commonly a plurality of thin, contoured diaphragms welded or otherwise secured together to form the coupling which is mounted to the driving and driven shafts.
Prior art coupling diaphragms have been designed with torque transmission as the primary consideration and flexibility as the secondary consideration. However, there are many applications in which torque transmission requirements are easy to achieve so that the flexibility requirement becomes the prime design factor. The flexibility feature of the diaphragm is incorporated in its profile.
It is well known that torque transmitting capacity varies as the reciprocal of the square of the radius of the diaphragm. For that reason prior art diaphragms have their thinnest section near their rim. However, this generates high stresses in the rim area under axial deflection or bending conditions. The present invention features a particular diaphragm profile which enables the diaphragm to be stretched to accommodate large axial deflections without over-stressing the diaphragm material. In order to accommodate this condition the diaphragm must be thin enough to be flexible at those areas where the diaphragm stress will be low. Further, the profile of the diaphragms must take into account the torque transmission requirements for the flexible coupling arrangement and the buckling stability of the coupling.
In the present invention the diaphragm profile is analytically optimized so that the bending moment developed by axial deflections is small at the thinnest section of the profile. This insures that stress levels are minimal throughout the diaphragm. Consequently, greater axial deflection and bending can be accommodated before diaphragm material fatigue and endurance limits are reached than has heretofore been the case.